Radio transmission system



F. 2 IQ36. w RUNGE ET AL 2,028,880

RADIO TRANSMI S S ION SYSTEM Filed May 27, 1935 INVENTOR W/L HELM BUN6 MAX POH0/V TSCl-l ATTORNEY Patented Jan. 28, 1936 2,028,880

UNITED STATES PATENT OFFICE RADIO TRANSMISSION SYSTEM Wilhelm Runge and Max Pohontsch, Berlin, Germany, assignors to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application May 27, 1933, Serial No. 673,168 In Germany June 16, 1932 1 Claim. (Cl. 250-2) An object of this invention is to provide a ences, this latter device actuates control means method of and apparatus for synchronizing whereby the frequency of the local oscillator is transmitters or broadcast stations working on caused to come in step again with the remote synchronized waves over wire lines. In the methcontrol-wave transmitter.

5 ods customarily used in the prior art and prac- The application of the invention as applied to tice, recourse is had to an audio frequency cona complete system is schematically illustrated trol note or wave which is supplied to the transby way of example in Figure 1. Figures 2 to '7 mitter or broadcast stations by way of wires, and inclusive illustrate different embodiments of elewhich there furnishes the carrier wave, after ments of the system which may be used in Fighaving been subjected to frequency multiplicaure 1. l0 tion in a plurality of stages; or else in one of the Referring to Figure 1, s denotes the master stations the carrier frequency is divided, reduced broadcast station where the frequency f is gen or sub-multiplied to result in the control wave erated and radiated. Associated with the genor note, and from the latter, by corresponding erator g is a frequency-divider equipment t frequency multiplication at the other stations, whereby a sub-harmonic ,f/n is produced from 15 the common carrier frequency is recovered or the sending frequency. The said sub-harmonic restored. This latter method necessitates an wave is transmitted by a cable It to the sub-sta essentially different construction from standard tion s. At the substation s there is likewise practice of the controlling transmitter station provided generator equipment 9 to produce a (master broadcaster) and the other stations opfrequency i. From the frequency generated 20 crating in synchronism. But still more serious at the generator outfit g and which is required is the disadvantage residing in the requisite freto have absolutely the same value as the transquency multiplication in both of the methods mitted frequency 1 coming in from the master hereinbefore referred to. Frequency multiplicabroadcaster station s, there is also formed a subtion methods and means, as known from actual harmonic f/n by means of the frequency sub- 3;,

practice, are hard to stabilize, and they require multiplier 73'. The sub-harmonic locally proa considerable amount of filter apparatus to elimduced by the frequency converter t, together inate disturbing side or stray waves. However, with the sub-harmonic transmitted by cable what is worse, all of these methods fail to afford from the master transmitter s is fed into a conany protection against the inevitable transient trol or check-up device p. According to the dis- 3o fluctuations of the controlling phase transmitcrepancy which may be discovered between the ted by the cable or line, and this is conducive to locally generated sub-harmonic and the subtransient disturbances in the synchronism. harmonic transmitted by way of the cable, there All of these drawbacks are obviated in the is occasioned action upon the generator outfit g present method in the following fashion: of the transmitter s. 3.3

All of the synchronized stations operate as self- For the purpose of producing the audio freexcited oscillation generators. The control note quency control note from the carrier wave, re- W v Serves merely for h P pose of insurcourse may be had, fundamentally speaking, to ing automatic stabilization rather than for the all known means of frequency division or subdirect production 0f the carrier wave. It is an multiplication, in other words, arrangements 40 easy matter to introduce into the mechanism for which cgmprise amplitudedependent imped frequency correction a time constant such that ances g" saturated homeomd choke coils;

r apid alterations in the contr o1 trequency Such i furthermore, arrangements for producing relaxatnose. t it fi i m i E tion waves, for example, means comprising glow remam.me e6 an arm o discharge (gaseous-conduction) lamps or multitmnsmltter Stamens the earner frequency 15 vibrators and finally also feed-back schemes of lowered or stepped-down to a sub-harmonic by division at the same ratio, and this sub-harmonic sultable sort such as Illustrated by Way of exwave is transmitted from one of the stations to amPle m 5 the other stations in the form of a control or Flgm'e 2 1s regeneratlve tube cn'cult Whlch 50 check up or Stabilizer frequency or wave and is roughly tuned to the sub-harmonic Wave f/n. at these other broadcast stations the same is fed The tube Operates at a point ju t before c tconjointly with the locally generated sub-haring would be initiated. There is further supplied monic to a suitable phase check-up or balance to the same a frequency f to serve for controlling 5 instrument. Upon the arising of phase diiferpurposes, with the result that the device is caused to start oscillating in such a way that the desired sub-harmonic wave ensues;

Phase comparison of the wave sent by way of a firmly inter-connected coils which are pivotally suspended within the field of a third coil. One of the voltages to be checked up upon, e is im-:

pressed upon the said crossed coils, buteunder a phase displacement angle oi! 90 degreees, whereas the other voltage e1 is applied to the fixed coil 61. The rotation of the mobile system is directly proportional to the phase difference between the two potentials, and is independent of the amplitude thereof.

There may further be considered for the sake of insuring a comparison of the phase a number of arrangements which are not predicated for their use upon any moving parts. this sort is illustrated, for instance, in Figure 4. The two voltages e1 and ez which are to be compared are supplied to; the primary windings (turns) of a diiferentiai type of transformer; a rectifier device includedin the secondary circuit results in a current which is directly proportional to the phase difference, if any. Of course, a device of this nature depends for its action upon the amplitude, hence, it necessitates prior amplitude regulation between the voltages to be compared.

A differential arrangement of the kind illustrated Figure 5 is i'ree from this difiiculty, One of the potentials is impressed upon the grids of the two rectifier tubes under isophasic condi; tion, whereas the other one is impressed in the presence of phase opposition. If, then, under normal condition, the two voltages have been so adjusted by a phase shifter to present a phase angle between each other of exactly 90 degrees,

equality of the resultant grid voltage amplitudes ya and ob will exist according to Figure 6, and. the same situation will hold trueof the plate currents of both tubes, and this regardless of the amplitudes of the two impressed potentials. Upon the arising of phase shifts, the state of balancebetween the two plate currents is disturbed, with the result: that there is effected a shift in the differential relay inreither direction, as the case may be.

The operation 01' the arrangement shown in Figure '7 is similar to that above described. The circuit of this figure comprises a soft-iron keeper between two iron-cored coils, one thereof being energized under co-phasic condition, and the other one in the presence of phase opposition. If

the voltages from the outset are again shifted 2,028,880 T j "1 f. i.

A scheme 0L an arigle of 90 degrees in reference to each other, there holds true also in this instance the diagram Figure 6; and because of the fact that the dependence between torque and coil currents obeys a square law, there prevails a similar relationship between such phase differences as may arise and theensuing torque exerted upon the keeper.

The phase comparison device, generally speaking, will result in an effect the size of which corresponds to the prevailing phase angle, and will thus prove serviceable for the purpose of automatically restoring synchronism. For instance, the said device may be caused to insure a mechanical control action whereby, for instance, the condenser included in the oscillation circuit of the local wave generator is re-adjusted; or else, in the case of transmitters subjected to quartz-crystal control, the temperature of the quartz thermostat could be controlled by the said phase equalizing or comparison device, with the consequence that thus a fine adjustment of the frequency is assured. Finally, also therfrequency of the local transmitter could be acted upon by electrical means and Ways. One method known in the prior art utilizes the regulator current for the saturating and thus the alteration of inductance of an iron-cored tuning coil; another method consists in that theregulator current is used to alter the grid biasing voltage and the internal resistance of a tube, the tube being synchronizing the frequency produced at said remote station which comprises generating a carrier wave at said master station, obtaining from said carrier a sub-harmonic" frequency, transmitting said sub-harmonic frequency over said .line to said remote transmitting station, locally generating at said remote transmitting station a carrier whose frequency approximates that of the carrier generated at said master station, obtaining front said local carrier at said remote station a sub-harmonic similar to that received from said master station, comparing the phase trolling the frequency of said locally generated carrier from the difference in phase existing between said two sub-harmonic frequencies.

WILHELM RUNGE.

MAX POI-IONTSCE.

relations of both said sub-harmonics and con- 

